The present invention is related to apparatus for selectively locking the angular position of a pivoted concrete chute relative to a vertical axis on the frame of a concrete mixing vehicle.
Concrete mixing and transporting vehicles typically include an angular rotating mixing drum that holds and agitates a wet mixture of concrete during transportation. The mixing drums normally have a capacity of between seven and ten cubic yards of concrete, which weighs approximately 4,000 pounds per cubic yard.
When the concrete is to be delivered, rotation of the drum is reversed to direct concrete outwardly through a rearward discharge. The discharged concrete is received and guided to the poursite by a pivoted chute. The chute is selectively positioned about a vertical axis on the vehicle frame to direct concrete to either side or to the rear of the mixing vehicle. Extensions are frequently employed for directing concrete to more remote locations.
Concrete, at 4,000 pounds per cubic yard, produces high stresses along the chute. Heavy concrete at the end of a long extension can produce severe torsional forces about the inner end of the chute. The chute therefore becomes very difficult to control manually and can easily slip from control, pivoting in whatever direction gravity dictates. A freely pivoted chute can result in the waste of both concrete and resultant man-hours needed for cleanup, and can also be a safety hazard for those working in the are a of the chute.
A properly operating chute brake system would enable selective angular positioning of the chute when released and positive locking of the chute at the selected angular position when actuated. Such a brake mechanism should be situated directly adjacent the pivot axis for the chute and directly adjacent the bearing surfaces.
Known forms of chute brake assemblies include a manual operable clamp assembly mounted to a pivoted chute brace. The brake consists of a threaded shaft at one end of an upright brace bearing shaft. A wheel is threadably engaged to the shaft and can be selectively tightened against the shaft journal to clamp the brace tightly to the vehicle frame. The brace-type brake is partially serviceable for standard length chutes. However, the locking mechanism can vibrate loose and allow the chute to pivot freely. Furthermore, the location of the brake mechanism below the actual bearing surfaces between the chute and the vehicle frame does not directly absorb the torque applied about the bearing axis.
It still remains desirable to obtain some form of positive brake mechanism that is easily controlled at the point of pivotal engagement between the frame and chute, to selectively lock the chute at any desired angular position.
U.S. Pat. No. 3,279,766 to F. V. Mendoza discloses a transit concrete mixer with particular reference to a brake mechanism. The mechanism disclosed enables selective angular positioning of a concrete chute. The brake components used are of typical automotive drum brake design with axially oriented shoes and brake surfaces. A hydraulic brake cylinder is utilized for actuation of the brake shoes selectively bringing them radially against a brake drum. The nature of the brake assembly dictates that the entire braking mechanism be mounted below the ring bearing that mounts the chute to the vehicle frame. Actually, the brake assembly replaces the standard hand rotatable brake wheel discussed above. The Mendoza brake therefore represents a simple mechanization of the manually operable brake with additional advantages of remote control ability and less chance of failure due to vibration of the chute and vehicle frame. Forces transmitted along the length of the chute are still directed primarily to the bearing surfaces of the chute above the brake mechanism. The low positioning of the brake therefore causes undesirable stresses along the brace mechanism. Excessive torsional stress would not be incurred if, somehow, the brake mechanism could be supplied adjacent the point of pivotal engagement between the frame and chute.
The problem of braking the pivoted chute at the pivotal mount for the chute is recognized to a limited degree in the U.S. Patent to Hansen et al, U.S. Pat. No. 3,334,872. Hansen et al discloses a double ended piston hydraulic cylinder that controls pivotal movement of a chute at the chute mounting point on the concrete mixing truck. The cylinder operates to pivot the chute about its axis and also acts as a positive brake.
The hydraulic cylinder requires use of an expensive and complex hydraulic system that is not typically supplied as standard equipment on concrete mixing trucks. Hydraulic cylinders wear quickly when exposed to concrete with its naturally abrasive component. Maintenance and repair therefore become frequent. Furthermore, use of a hydraulic cylinder could be considered "overkill", since the primary need is not for powered movement of the chute. The chute is usually empty when moved from one position to another. The primary need is for holding the chute stationary after being angularly positioned, when it is full of heavy concrete.
U.S. Pat. No. 3,410,538 to M. L. Potter discloses a positive locking apparatus for positioning a concrete chute at any of several preselected angular positions. Potter's arrangement uses a positive detent type lock between the chute frame and a plate pivoted with the chute. A pin is used to interconnect the stationary frame with the pivoted plate by insertion within one of several angularly spaced apertures provided in the movable plate.
The Potter device and other known "detent" type chute locking mechanisms do allow positive positioning of the chute at the pivot point between the chute and stationary frame but do not enable infinite angular adjustment for precise pouring. Further, such mechanisms will not effectively operate to stop a moving chute without causing possible damage to the lockout mechanism. Difficulty is also experienced in removing and placing the lock pin when the chute is loaded.
The present invention includes a brake mechanism that can be mounted to existing chute and frame arrangements and that makes use of the existing pneumatic systems typically available for air brakes on the mixing vehicle. The present brake mechanism can be controlled to stop the chute at any selected angular position and hold it securely in place until deactuated. The present brake does not include inherent capability to pivot the chute about its axis and is therefore extremely simple in construction and easy to operate and maintain.